Analysis of ground-motion spatial variability at very local site near the source AFIFA IMTIAZ Doctorant ( ), NERA Project

MEEES Master Research GROUND MOTION VARIABILITY from NUMERICAL SIMULATION & COMPARISON WITH THE ANALYSIS OF REAL DATA To address the issue of ground motion variability from synthetic simulation, especially in the near field To capture some physical explanation on the parameters influencing ground motion variability To compare the obtained results with the observations based on accelerometric database

Master Research APPROACH -Evaluation of Single Station WITHIN-event variability of ground motion - By performing numerical simulation based on realistic description of the different rupture processes at a given site  Strike-Slip events on vertical fault  Chosen Magnitudes : Mw 6.67 and 5.0  Chosen Distances (JB): 1, 3, 10, 30, 60 km  Homogeneous and Heterogeneous Slip Models  Ground Motion in terms of PGV

PGV Attenuation with Distance 1. Initially at close distances PGV gradually increases, but then rapidly decreases with distance 2. The deeper the hypocentre the farther the PGA maxima in near field 3. For same source, variation in focal depth has no influence on PGV amplitudes in the far field Possible Explanation: S-wave radiation pattern and then gradual wave attenuation effects at far field

PGV Variability for Extended Source Mw 6.7 Extended Fault ObservationPossible Explanation High variability at 1 km distanceSlip distribution dominates Smaller variability at 3 and 10 km distance Decrease in the effect of source capacity and less dominating radiation pattern Increase in variability in far fieldEffect of radiation pattern Larger variability is associated with the rough model in near field, but the difference with other model is small Probably because station network is not dense enough to catch small scale variability of slip distribution

Point-source Mw 5.0 Mw 6.7 PGV Variability Summary 1. Sigma is highly dependent on Magnitude and Distance 2. Smaller event (Mw 5.0) has higher intra-event variability at short distances

Observations from Real Data Analysis Site corrected intra-event variability with magnitude and distance Proposed single station intra-event variability model Site corrected intra-event variability decreases with the increase in magnitude and distance Rodriguez-Marek et al Courtesy : Fabrice Cotton

Conclusions from the Research Our Results show that the INTRA-event variability is magnitude and distance dependent We observed that variability decreases with the increase in distance and magnitudes For large extended faults, the near field variability is captured by the details of slip distribution In the far field, the variability seems to be dominated by the radiation pattern of S waves Main conclusions are confirming the results coming from real data

Doctorant Research EFFECTS OF SURFACE GEOLOGY & GEOMETRY ON AMPLIFICATION & VARIABILITY OF EARTHQUAKE GROUND MOTION - EXPERIMENTAL & NUMERICAL APPROACH to understand the key subsoil parameters that locally control the strain values and the spatial variability of ground motion to develop and calibrate simple, engineering-oriented, correlations or models that could allow to incorporate basin and surface topography effects in seismic design (building codes, microzonation studies etc.).

Goals 1.to perform extensive, parametric numerical simulations on 2D and simple 3D basin models with varying mechanical, geometrical characteristics, and incoming wavefields 2. to analyze the ground motion and strain synthetics in order to investigate the link between ground motion parameters, strains, seismic wavefield, source closeness and complexity and subsurface properties. - The numerically derived estimates of ground motions and strains will be compared to actual specific measurements of spatial variability and strains Doctorant Research

Brief Schedule Year 1: - Modeling ground motion variability in near-field. Continuation of the research started in Master for varied models and earthquake magnitudes. - Installation and Monitoring of seismic experiments in Greece (September March 2012) and Italy (March July 2012). - Preliminary data analysis. -Handling and early 2D modeling of the seismic response of sedimentary valleys. Year 2: - Analysis of Greek and Italian experimental data (analysis of the wave field, differential movement, spatial variability, site effects). -Further modeling and 2D sensitivity analysis (characteristics of the amplification versus seismic characteristics of the seismic loading characteristics mechanical and sedimentary fillings). Year 3: -3D modeling and experimental comparison site observation-modeling. - Writing papers and PhD thesis. Doctorant Research

SEISMOTECTONICS -situated in Northwestern- most boundary of Aegean Plate -Dominated by Cephalonia Transform Fault (CTF) -The rate of seismic slip in CTF: ~3cm/yr, highest in Aegean area Ongoing Field Experiment Argostoli, Kefalonia Island, Greece Strike Slip Faults N-S Extension E-W Extension Plate subduction Continental Collision Greece

Current Seismicity of Argostoli, Kefalonia Argostoli

Locations of ISTerre Seismic Stations Total 25 stations installed in Sep 2011 S01, S03...: Alluvium 50 m linear distance A00, A01, A02,..., A20: Array on 5, 15, 25, 50 m radii